EW-I-1+2: Weather-related disruptions in and unavailabilty of power supply | Umweltbundesamt

EW-I-1: Weather-related disruptions in power supply

Until 2010, extreme weather events such as hurricanes Cyril (2007) and Xynthia (2010) stood out clearly among weather-related disruptions of power supply; low-pressure related storms that occurred thereafter, such as Friederike (2018) and Bernd (2021), do not stand out in the same way. As far as low voltage is concerned, the proportion of weather-related disruptions declined significantly from 2006 onwards whereas in respect of medium voltage the proportion rose again lately.

EW-I-2: Weather-related unavailability of electricity supply

In 2021 the highest value amounting on average to just under 23 minutes per end consumer was reached in respect of weather-related unavailability of electricity supply in Germany. This outcome was caused primarily by the impacts of the low-pressure system Bernd in July 2021. While the unavailability of electricity owing to other unscheduled disruptions is declining, there is so far no significant trend discernible for weather-related causes.

Extreme weather events affect the electricity supply

Overall, Germany’s electricity supply is very reliable. It is characterised by the fact that disruptions are infrequent and very brief. In Germany, the Federal Network Agency (BNetzA) keeps records of any disruptions. As part of its remit the BNetzA evaluates reports made by grid operators on disruptions of more than three minutes’ duration regarding medium- and low-voltage supply which make up the distribution network for the consumer. The BNetzA differentiates between various causes of disruption in the supply network. For example, the agency categorises wind and temperature effects or overvoltages due to lightning strikes collectively as ‘atmospheric impacts’. Events of particular severity such as extraordinary floodwater or hurricanes are classified as ‘force majeure’. Such events, in particular, can entail prolonged adverse effects; for example when grids are disrupted over long distances, essential repairs can sometimes take a long time. Nevertheless, transmission and distribution of electricity can be affected by extreme weather events and weather patterns in Germany, despite this being one of the most stable power supply systems in the world. The impacts of hurricane Cyril in 2007 were particularly striking. In that year, the proportion of weather-related disruptions was more than twice the average recorded for the period from 2006 until 2021, both at the level of low-voltage and medium-voltage supply. No similarly high value has been reached since then. In 2007 end consumers had loss of electricity – within the meaning of the EnWG – on average just under 22 minutes at a time, resulting from weather-related and weather-pattern related events; in most years this value amounts to less than 10 minutes.

In other years there is no such direct correlation between the number of disruptions and their cumulative duration. In 2013 for example, the electricity supply had to be switched off temporarily owing to flooding in some of the power supply areas, which meant that end consumers were without electricity for on average approximately 20 minutes nationwide. Likewise, the heavy rainfall events caused by the low-pressure system Bernd in July 2021 brought about extreme flooding in some river basins. For example, the floods reached several electricity substations which had to be shut down for safety reasons. This resulted in large-scale power outages, temporarily affecting more than 100.000 households. With periods of just under 23 minutes on average nationwide, the weather-related unavailabity of electricity reached the highest value hitherto. The number and proportion of weather-related disruptions was less conspicuous in those two years.

If extreme weather situations – such as severe storms, hurricanes and heavy rain events – become more frequent owing to climate change, associated disruptions in power supply may become more frequent and their duration may increase, unless networks are appropriately engineered and maintained. Whether electricity networks become affected depends, apart from atmospheric impacts, also on the quality, maintenance condition and age of technical components used in the network. Since 2010 investments in and expenditure on new installations, expansion, extensions, maintenance and upgrades have distinctly increased. Some 10 billion Euros have been invested in the German electricity network annually since 2015; in 2021 the investment amounted to some 13.6 billion Euros.^{157 157} The condition of power lines, transformers and circuit breakers contained in the electricity network is therefore estimated to be functionally appropriate.

Another key determinant is the network structure. To date, approximately 91.5 % of extra-high and high-voltage transmission lines are routed above ground thus being directly exposed to wind and weather. However, the nodes of this grid are interconnected (meshed). A high degree of meshing contributes to high reliability of supply. In case of the failure of individual lines, the supply can usually be re-routed via other, so-called redundant lines (n-1- safety). This is why the end consumer does not usually suffer any power outages from disruptions in the transmission network. Effective protection from storms, snow loads or ice loads can be achieved by routing electricity lines (cabling), in particular medium- and high-voltage lines, underground. At the extra-high voltage level, priority has been given since 2015 – as embedded in the planning principles of Federal sectoral planning – to underground cabling of extra high voltage direct current transmission lines (HGÜ). Apart from increasing the acceptance of the network expansion, this can also improve the resilience of networks to climate-change related impacts. Concurrently, there is ongoing research on selected pilot routes in order to identify to what extent underground cabling might be used with regard to three-phase current lines.

^{157 - BMWi – Bundesministerium für Wirtschaft und Energie (Hg.) 2021: Die Energie der Zukunft. 8. Monitoring-Bericht zur Energiewende – Berichtsjahre 2018 und 2019. Berlin, 289 pp. https://www.bmwk.de/Redaktion/DE/Publikationen/Energie/achter-monitoring-bericht-energie-der-zukunft.html}

^{BNetzA – Bundesnetzagentur, BKartA – Bundeskartellamt (Hg.) 2023: Monitoringbericht 2022. Marktbeobachtung Monitoring-Energie. Bonn, 543 pp. https://www.bundesnetzagentur.de/SharedDocs/Mediathek/Monitoringberichte/MonitoringberichtEnergie2022.pdf}